Method and apparatus for magnetic printing

ABSTRACT

A magnetic transfer method includes a first step (ST 103 ) of preparing a magnetic disk, a second step (ST 105 ) of forming a layer of lubricant on the magnetic disk, a third step (ST 108 ) of bringing a surface of the magnetic layer on the magnetic disk into close contact with a magnetic transfer master having a magnetic film formed on at least one side and magnetically transferring a pattern of the magnetic film on the magnetic transfer master onto the surface of the magnetic disk through application of an external magnetic field, and a fourth step (ST 104,  ST 106 ) of burnishing at least a surface of the magnetic disk that comes into contact with the magnetic transfer master. The first step, the fourth step, the second step, the fourth step, and the third step are performed in the stated order.

TECHNICAL FIELD

The present invention relates to a method for magnetically transferringa signal onto magnetic disks such as those used in hard disk drives andfloppy disk drives, and to an apparatus that uses this method.

BACKGROUND ART

In the field of magnetic recording/reproduction apparatuses, there is atrend towards the use of higher recording densities with the aim ofproducing small, high-capacity apparatuses. A representative example ofa magnetic recording/reproduction apparatus is a hard disk drive. Harddisk drives with areal recording densities in excess of 10 GBit/in²already have appeared on the market, with 20 Gbit/in² drives beingexpected in the next few years due to the rapid technologicaladvancements being made in this field.

A major factor in the achievement of high recording densities is the useof magneto-resistive type heads that allow increases in linear recordingdensity and can reproduce, with a favorable S/N ratio, a signal recordedon a track no wider than a few microns.

The increases in recording density also have made it necessary to reducethe distance that a floating magnetic slider floats above the surface ofa magnetic disk. This increases the probability of the slider collidingwith the disk due to a variety of causes. Such a situation requires thatmagnetic disks be made with smoother surfaces.

Tracking servo technology used in a head also plays an important role inhaving a head precisely follow a narrow track. Modern hard disk drivesthat use such tracking servo technology have areas in which trackingservo signals, address information signals, reproduction clock signalsand the like are recorded that are provided on magnetic recording mediaat intervals of a predetermined angle, (also called “preformat recordingareas” in the following). A drive apparatus detects the position of thehead from the above signals that are outputted by the head atpredetermined time intervals, and corrects the head position so that thehead can properly follow a track on the disk.

The servo signals, address information signals and reproduction clocksignals therefore are used as reference signals in order to have thehead properly scan tracks on the disk. As a result, high positionalaccuracy is required when writing these signals onto a disk (suchwriting is hereafter referred to as “formatting” the disk). For currenthard disk drives, the recording head is positioned during formattingusing a dedicated servo apparatus equipped with a highly preciseposition detecting apparatus that uses optical interference (hereaftersuch servo apparatuses are referred to as “servo writers”).

However, formatting using an aforementioned servo writer has thefollowing drawbacks.

Firstly, recording by a magnetic head is linear recording where there isrelative movement between the magnetic head and the magnetic recordingmedium. Since it is necessary to record signals on a large number oftracks, preformatting using a servo writer takes a long time. To makemanufacturing more efficient, several expensive, dedicated servo writersneed to be provided, making the preformatting operation very costly.

Secondly, the implementation and maintenance of many servo writersincurs a high cost. This cost becomes more severe as the track densityand number of tracks increase.

As a result, a different formatting method that does not use servowriters has been proposed. With this method, a disk called a “master” onwhich all of the servo information is recorded is placed on top of themagnetic disk to be formatted and energy to achieve transfer is appliedfrom an external source to transfer all of the master information ontothe magnetic disk.

One example of this technique is the magnetic recording apparatus taughtby Publication of Unexamined Japanese Patent Application JP H10-40544A.According to this application, a magnetic portion made from aferromagnetic material is formed in a pattern corresponding to aninformation signal on a substrate surface, thereby producing a masterinformation carrier. The surface of this master information carrier isbrought into contact with the surface of a magnetic recording medium.This magnetic recording medium may be in the form of a sheet or a disk,and is provided with a ferromagnetic thin film or an applied layer of aferromagnetic powder. A predetermined magnetic field is then applied, sothat a magnetic pattern corresponding to the information signals formedon the master information carrier is recorded on the magnetic recordingmedium.

With the above method, the arrangement of patterns corresponding to theinformation signals on the master information carrier can be recordedsimultaneously onto the magnetic recording medium as magnetic patterns.When recording information signals using this kind of magnetic transferapparatus, it is important to have the information signals recordeduniformly and with high stability across the entire surface of themagnetic recording medium. However, when unwanted protrusions or foreignmatter are present at the interface of the magnetic recording medium andthe master information carrier, depressions appear in the surface of themagnetic recording medium when the magnetic recording medium comes intocontact with the master information carrier.

FIG. 18 shows a graph produced by measuring a cross-section of adepression appearing after the magnetic recording medium and masterinformation carrier have been brought into contact and magnetic transferhas been carried out with a conventional magnetic transfer method. Asshown in FIG. 18, the depression is about 50 nm deeper than the surfaceof the magnetic recording medium, and is surrounded by a slightprotrusion that is about 20 nm high.

A floating magnetic slider generally floats about 20 nm above thesurface of a magnetic recording medium. If, like the medium shown inFIG. 18, a magnetic recording medium has protrusions that are 20 nmhigh, the magnetic head will come into contact with the magneticrecording medium during the recording and reproduction of data. Whenthis happens, the impact forces the magnetic head upward, increasing theclearance between the magnetic head and the magnetic recording mediumand worsening the signal recording/reproduction performance. Also,physical contact between the magnetic head and the magnetic recordingmedium shortens the life of the magnetic head and can lead to diskfailures for the magnetic recording medium.

FIG. 19 is a depiction of the measurements produced by opticallymeasuring protrusions across the entire surface of a magnetic recordingmedium on which information has been magnetically transferred using aconventional magnetic transfer method. As can be seen, a large number ofprotrusions 20 nm or higher are present on the surface of the magneticrecording medium.

As described above, magnetic transfer according to conventional magnetictransfer methods often results in a large number of protrusions beingpresent on the magnetic disk after the magnetic transfer. This causesthe problems of lower recording/reproduction performance of the magneticrecording medium and a shorter lifespan for a magnetic head. If themoves towards higher recording densities are accompanied by a reductionin the distance that a magnetic head floats above a magnetic recordingmedium, these problems will become more severe.

DISCLOSURE OF INVENTION

It is an object of the present invention to provide a highly reliablemagnetic transfer method that solves the above problems that occur withconventional methods, and that suppresses the occurrence of minuteprotrusions on a magnetic disk.

The magnetic transfer method of the present invention includes a firststep of preparing a magnetic disk; a second step of forming a layer oflubricant on the magnetic disk; a third step of bringing the magneticdisk into close contact with a magnetic transfer master having amagnetic film formed on at least one side and magnetically transferringa pattern of the magnetic film on the magnetic transfer master onto themagnetic disk through application of an external magnetic field; and afourth step of burnishing at least a surface of the magnetic disk thatcomes into contact with the magnetic transfer master. The first step,the fourth step, the second step, the fourth step, and the third stepare performed in the stated order.

With this method, a burnishing process is performed on the surface of amagnetic disk before magnetic transfer, so that unwanted protrusions andforeign matter are removed from the surface of the magnetic disk,thereby making highly reliable magnetic transfer possible.

Another magnetic transfer method of the present invention includes astep of bringing a magnetic disk into close contact with a magnetictransfer master having a magnetic film formed on at least one side; astep of magnetically transferring a pattern of the magnetic film on themagnetic transfer master onto the magnetic disk through application ofan external magnetic field; and a step of optically detecting defects inthe surface of the magnetic disk. The magnetic transfer step isperformed immediately after confirming in the optically detecting stepthat one of a number of defects on the surface of the magnetic disk anda size of the defects on the surface of the magnetic disk is not greaterthan a predetermined value.

With the above method, the magnetic transfer is performed immediatelyafter confirming that there are no defects on the surface of themagnetic disk. This makes it is possible to perform highly reliablemagnetic transfer where defects are not produced in the surface of themagnetic disk.

Yet another magnetic transfer method of the present invention includes asteps of bringing a magnetic disk into close contact with a magnetictransfer master having a magnetic film formed on at least one side; astep of magnetically transferring a pattern of the magnetic film on themagnetic transfer master onto the magnetic disk through application ofan external magnetic field; and a step of detecting defects in themagnetic disk by scanning the magnetic disk with a detection head thatfloats a predetermined distance above the surface of the magnetic disk.The detecting step is performed after the magnetic transfer step.

The above method provides a highly reliable magnetic transfer methodwhere defects are not produced in the surface of a magnetic disk due tomagnetic transfer, and can supply magnetic disks that have no surfacedefects.

Other magnetic transfer methods in the following all include a defectdetecting step for detecting defects in a disk, in addition to a basicmagnetic transfer process of bringing a magnetic disk into close contactwith a magnetic transfer master having a magnetic film formed on atleast one side, and magnetically transferring a pattern of the magneticfilm on the magnetic transfer master onto the magnetic disk throughapplication of an external magnetic field.

In one of these other magnetic transfer methods, after the defectdetecting step has confirmed that one of a number of defects on thesurface of a cleaning disk and a size of the defects on the surface ofthe cleaning disk is not greater than a predetermined value, thecleaning disk is brought into close contact and separated from themagnetic transfer master a predetermined number of times, before themagnetic transfer master is brought into close contact with the magneticdisk and magnetic transfer is performed.

With the stated method, foreign matter that adheres to the magnetictransfer master can be quickly and reliably removed, thereby making themagnetic transfer method highly reliable.

In another of these other magnetic transfer methods, after a cleaningdisk is brought into close contact and separated from the magnetictransfer master a predetermined number of times, the magnetic transfermaster is brought into close contact with a detection disk, thedetection disk having been subjected to the defect detecting step toconfirm, for a surface of the detection disk that comes into contactwith the magnetic transfer master, that one of a number of defects and asize of the defects is not greater than a predetermined value, and thedetection disk is then subjected to the defect detecting step and whenthe defect detecting step confirms that one of a number of defects on asurface and a size of the defects is not greater than a predeterminedvalue, the magnetic disk and the magnetic transfer master are broughtinto close contact and magnetic transfer is performed.

Thus, the detection of defects on the magnetic transfer master can beperformed easily and with very high precision, thereby making themagnetic transfer method highly reliable.

In yet another of these other magnetic transfer methods, the magnetictransfer master is brought into close contact and separated from acleaning disk a predetermined number of times, the cleaning disk havingbeen subjected to the defect detecting step to confirm, for a surface ofthe cleaning disk that comes into contact with the magnetic transfermaster, that one of a number of defects and a size of the defects is notgreater than a predetermined value. The magnetic transfer master is thenbrought into close contact with a detection disk, the detection diskhaving been subjected to the defect detecting step to confirm, for asurface of the detection disk that comes into contact with the magnetictransfer master, that one of a number of defects and a size of thedefects is not greater than a predetermined value, and the detectiondisk is then subjected to the defect detecting step and when the defectdetecting step confirms that that one of a number of defects on asurface and a size of the defects is not greater than a predeterminedvalue, the magnetic disk and the magnetic transfer master are broughtinto close contact and magnetic transfer is performed.

In yet another of these other magnetic transfer methods, after thepattern of the magnetic film on the magnetic transfer master has beenmagnetically transferred onto the magnetic disk, the magnetic disk issubjected to the defect detecting step, and when one of the number ofdefects and size of defects is equal or greater than a predeterminedvalue, the magnetic transfer master is brought into close contact withand separated from a cleaning disk a predetermined number of times.

Thus, foreign matter that adheres to the magnetic transfer master can bedetected quickly and easily, before being removed. As a result, magnetictransfer can be performed with highly reliability.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flowchart showing the various processes performed in themagnetic transfer method of the first embodiment of the presentinvention.

FIG. 2 shows a magnification of part of the magnetic transfer masterused in the present method.

FIG. 3 is a cross-sectional drawing showing an apparatus used in stepST102 of the present method during a separating operation.

FIG. 4 shows the apparatus of FIG. 3 during a pressing operation.

FIG. 5 is a top view of the magnetic transfer master used in the firstembodiment.

FIG. 6 is a top view of the boss used in the apparatus shown in FIG. 3and in FIG. 4.

FIG. 7 shows the relationship between the passage of time and airpressure in a gap S formed by the apparatus shown in FIG. 3 and in FIG.4.

FIG. 8 shows a tape burnishing step ST104 included in the magnetictransfer method of the first embodiment.

FIG. 9 is a simplified cross-sectional view of an apparatus thatperforms step ST107 and step ST108 of the present method.

FIG. 10 is a cross-sectional view of an apparatus that performs stepST108 of the present method during a separating operation.

FIG. 11 is a cross-sectional view of the apparatus that performs stepST108 of the present method during a pressing operation.

FIG. 12 is a perspective view showing an apparatus for performing aglide height test in the present method.

FIG. 13 shows experimental results obtained by investigating defects ona magnetic disk and signal errors for various magnetic disk conditioningmethods.

FIG. 14 is a flowchart showing the processes used in a second embodimentof the present invention.

FIG. 15 is a cross-sectional drawing showing an apparatus used in stepST202 of the present method during a separating operation.

FIG. 16 shows the apparatus of FIG. 15 during a pressing operation.

FIG. 17 shows a relationship between a number of times a magnetictransfer master and a cleaning NiP disk were pressed together andseparated and a number of defects in the surface of the cleaning NiPdisk.

FIG. 18 is a cross-sectional view of a depression in a magnetic diskafter magnetic transfer according to a conventional method.

FIG. 19 shows measurements produced by optically measuring the surfaceof the magnetic disk after the conventional magnetic transfer.

BEST MODE FOR CARRYING OUT THE INVENTION

The following describes the preferred embodiments of the presentinvention with reference to the accompanying drawings.

First Embodiment

The following describes a magnetic transfer method and magnetic transferapparatus according to the first embodiment of the present invention,with reference to FIGS. 1 to 11.

FIG. 1 shows the flow of a process for magnetic transfer, including aprocess for manufacturing and conditioning the magnetic disk. First, amaster disk used for the magnetic transfer is described.

FIG. 2 is an enlarged view of part of a magnetic transfer master disk 2showing the disk configuration. In FIG. 2, numeral 30 indicates amagnetic film that enables a magnetic pattern to be transferred onto amagnetic disk. A master information pattern is formed on this magneticfilm 30, in a pattern corresponding to the digital information signal tobe recorded on the magnetic disk. This master information pattern isformed in a magnetic portion made up of a ferromagnetic thin film.Radial grooves 4 are also provided on the same contact surface 3 as themagnetic film 30.

Various types of magnetic materials can be used for the ferromagneticthin film, such as hard magnetic materials, semihard magnetic materials,or soft magnetic materials. Any material that enables a digitalinformation signal to be recorded on the magnetic recording medium maybe used. As examples, iron, cobalt, or an alloy of iron and cobalt maybe used.

In order to produce a sufficient magnetic field for transferring themaster information regardless of the magnetic disk type, the saturationmagnetic flux density of the magnetic material should be as high aspossible. In particular, for magnetic disks that have a high coercivityin excess of 2000 oersted, or large flexible disks with a thickrecording layer, there are cases where a saturation magnetic fluxdensity of 0.8 tesla or below is not sufficient for recording to beperformed properly. For this reason, a magnetic material with asaturation magnetic flux density of 0.8 tesla or above, or preferably1.0 tesla or above, is used.

As shown in step ST101 in FIG. 1, the magnetic transfer master 2 of theabove configuration is washed using a conventional method, such asscrubbing. However, it has been found by experimentation that using aconventional washing, it is not possible to remove minute unwantedprotrusions in the magnetic film 30 that remain in the contact surface 3of the magnetic transfer master 2 or minute particles of foreign matterwhose sizes range from about 20 to 50 nm. For this reason, step ST102 isperformed to completely remove such minute particles of foreign matter.In step ST102, the magnetic transfer master disk and a cleaning NiP diskare pressed closely together and separated a predetermined number oftimes. This step ST102 is described below with reference to FIGS. 3 and4.

FIGS. 3 and 4 are cross-sectional drawings showing the apparatus thatperforms step ST102 and the operation of this apparatus. FIG. 3 showsthe apparatus during the separation operation, while FIG. 4 shows theapparatus during the pressing operation. In these drawings, numeral 1Aindicates the cleaning NiP disk, while numeral 2 indicates the magnetictransfer master disk that is pressed against the surface of the cleaningNiP disk 1A.

Numeral 3 indicates the surface of the magnetic transfer master 2 thatcomes into contact with the cleaning NiP disk 1A. Grooves 4 are providedin this contact surface 3. FIG. 5 is a top view of the contact surface3. As shown in FIG. 5, the grooves 4 extend radially from the center ofthe magnetic transfer master 2. In the present embodiment, the grooves 4are about five microns deep. Numeral 5 indicates a boss that is fixed tothe center of the magnetic transfer master 2. The boss 5 engages acenter hole of the cleaning NiP disk 1A, and so centers the magnetictransfer master 2 and the cleaning NiP disk 1A. Also, as shown in FIG.6, predetermined gaps 51 are provided between the center hole of thecleaning NiP disk 1A and the boss 5, thereby allowing air to passbetween them.

In FIGS. 3 and 4, numeral 6 indicates a support for supporting thecleaning NiP disk 1A. A through hole 7 is provided in the center of thesupport 6 to allow the passage of air. Numeral 8 indicates an air ductthat expels air from between the magnetic transfer master 2 and thecleaning NiP disk 1A or pumps air between the two disks. Numeral 9indicates an exhaust outlet for allowing the air expelled by the airduct 8 to escape, numeral 10 indicates a suction pump that is connectedto the exhaust outlet 9, and numeral 11 indicates an exhaust valve thatcontrols the expulsion of air. Numeral 12 indicates an air supplyingpump for pumping air into the air duct 8, while numeral 13 indicates anair supplying valve for controlling the supplying of air. The airsupplying pump 12 is provided with a 0.01 micron air filter, so thatparticles of foreign matter that are 0.01 microns or larger in size arenot pumped into the air duct 8. Numeral 14 indicates a holding arm thatholds the magnetic transfer master 2. This holding arm 14 is fixed tothe magnetic transfer master 2. A boss formed at the top of the holdingarm 14 is supported by a guide member 16 so as to position the holdingarm 14 with the holding arm 14 free to slide in the vertical direction.

The following describes the separation and pressing operations indetail, with reference to FIGS. 3 and 4.

First, the separation of the disks through the supplying of air isdescribed with reference to FIG. 3. During this operation, the airsupplying pump 12 is operated with the exhaust valve 11 closed and theair supplying valve 13 open, so that air flows into the air duct 8. As aresult, air is pumped through the through hole 7 upward, which is tosay, in the direction shown by the arrow A in FIG. 3. The air that ispumped through the through hole 7 presses the boss 5 upward. Air is alsopumped into the grooves 4, as shown by the arrows B. This air that ispumped into the grooves 4 spreads out radially from the center of themagnetic transfer master 2 via the grooves 4. The air then passesthrough the gap between the magnetic transfer master 2 and the cleaningNiP disk 1A and escapes to the atmosphere. This flow of air carries anyfine particles of foreign matter that adhere to the surface of themagnetic transfer master 2 or the cleaning NiP disk 1A out of theapparatus.

FIG. 7 shows the relationship between the passage of time and the airpressure of the air in the gap (hereafter referred to as “gap S”)between the magnetic transfer master 2 and the cleaning NiP disk 1A. Asshown in FIG. 7, separation of the disks through the pumping of airbegins after three seconds. As a result, the air pressure of the air inthe gap S sharply increases from a pressure of 101.3 kPa. After aboutone second, a pressure of about 130 kPa is maintained. This periodcorresponds to the separation of the magnetic transfer master 2 and thecleaning NiP disk 1A.

During this operation, it is preferable for the gap between the cleaningNiP disk 1A and the magnetic transfer master 2 to be set as narrow aspossible. In the present embodiment, the gap is set at about 0.5 mm.

This increases the speed at which air flows between the cleaning NiPdisk 1A and the magnetic transfer master 2, ensuring that fine particlesof foreign matter present between the two disks are carried out of theapparatus.

In the present embodiment, the distance between the cleaning NiP disk 1Aand the magnetic transfer master 2 is controlled by having the uppersurface of the holding arm 14 touch the lower surface of the guidemember 16 just when the magnetic transfer master 2 and the holding arm14 have risen by 0.5 mm from the positions they hold when the cleaningNiP disk 1A and magnetic transfer master 2 are pressed together.

Next, the pressing together of the disks through the evacuation of airis described with reference to FIG. 4. During this operation, the airsupplying pump 12 is stopped and the air supplying valve 13 is closed.As a result, the holding arm 14 to which the magnetic transfer master 2is attached falls under its own weight, and the boss 5 engages thecenter hole of the cleaning NiP disk 1A, thereby mounting the cleaningNiP disk 1A. After this, the exhaust valve 11 is opened and the suctionpump 10 is operated.

Due to the above operations, air flows through the through hole 7downwards, in the direction shown by the arrow C in FIG. 4. The air inthe grooves 4, which is to say the air in the gap S, also flows throughthe gap between the center hole of the cleaning NiP disk 1A and the boss5, resulting in the air pressure in the grooves 4 that are covered bythe cleaning NiP disk 1A falling below atmospheric pressure. Thereforethe cleaning NiP disk 1A is pressed onto the magnetic transfer master 2mainly by atmospheric pressure 15.

As a result, foreign matter present on the cleaning NiP disk 1A issandwiched between the cleaning NiP disk 1A and the magnetic transfermaster 2. Since the cleaning NiP disk 1A is manufactured using a softermaterial than the magnetic transfer master 2, foreign matter that issandwiched between the two disks sinks into the cleaning NiP disk 1A orcauses depressions in the cleaning NiP disk 1A, without damaging thesurface of the magnetic transfer master 2. Unintended minute protrusionsin the magnetic transfer master 2 are also flattened when the magnetictransfer master 2 is pressed against the cleaning NiP disk 1A. In FIG.7, the period that follows the start of evacuation at zero seconds andduring which the air pressure in the gap S is about 30 kPa correspondsto the time in which the disks are pressed together.

Following the pressing operation, the separating operation shown in FIG.3 is repeated. That is to say, the exhaust valve 11 is closed, the airsupplying valve 13 is opened, and the air supplying pump 12 is operated.This results in air being pumped in the directions shown by the arrows Aand B in FIG. 3. The air pumped in this way forces the magnetic transfermaster 2 upward until the upper surface of the holding arm 14 comes intocontact with the lower surface of the guide member 16. At this point,air passes through the grooves 4 and continues to be pumped radiallyoutwards from the center of the magnetic transfer master 2 to the outerperiphery of the disk, as shown by the arrows B. As a result, foreignmatter that is present on the surface of the magnetic transfer master 2is expelled to the atmosphere together with the air pumped by the airsupplying pump 12, or is transferred onto the cleaning NiP disk 1A. Byrepeating the pressing together and separating operations apredetermined number of times, foreign matter can be removed from thesurface of the magnetic transfer master 2.

The following describes the method by which a magnetic disk 1 ismanufactured and conditioned.

First, as shown by step ST103 (sputtering), a magnetic layer is formedon the surface of a substrate using a conventional method. As oneexample, this magnetic layer can be formed by subjecting an aluminumsubstrate to a dry plating method, such as vapor deposition orsputtering. Conventionally, this magnetic layer is protected by forminga protective layer on top of the magnetic layer using dip coating, spincoating, or a dry plating method, such as vapor deposition orsputtering.

Following step ST103, in step ST104 tape burnishing is performed. Thisprocess is described below with reference to FIG. 8. FIG. 8 shows howtape burnishing is performed in the present embodiment of the presentinvention. This process is performed using a spindle 55 for rotating themagnetic disk 1, lapping tape 56 for removing protrusions from thesurface of the magnetic disk 1, and a nozzle 58 for supplying air 57that presses the lapping tape 56 against the magnetic disk 1.

First, the magnetic disk 1 is rotated and air 57 is supplied by thenozzle 58 to press the lapping tape 56 against the magnetic disk 1. Atthe same time, the lapping tape 56 is moved in the direction shown bythe arrow P in FIG. 8 and so removes protrusions from the surface of themagnetic disk 1. In this burnishing process, lapping tape 56 with anaverage granular surface roughness of 1.0 microns was used. The pressureapplied by the lapping tape 56 onto the surface of the magnetic disk 1was set at 400 kPa. If the pressure is too high, the surface of themagnetic disk 1 may be damaged. If the pressure is too low, the effectof burnishing is not sufficient. This process is able to remove unwantedprotrusions that are present on the surface of the magnetic disk 1following the formation of the protective layer.

The average granular surface roughness of the lapping tape 56 ispreferably within the range from 0.1 microns to 5.0 microns. If theaverage granular surface roughness is below 0.1 microns, the burnishingmay not be performed effectively. If the average granular surfaceroughness is above 5.0 microns, the surface of the magnetic disk 1 maybe damaged. As an abrasive layer for forming the granular surface of thelapping tape 56, it is preferable to use a hard abrasive such asα-Al₂O₃, SiO₂, diamond and so on. If the abrasive layer does not includea hard abrasive, the effect of burnishing is not sufficient.

A support member of the lapping tape 56 may be a film made of polyesterresin such as polyethylene terephthalate (PET), polyolefin resin such aspolypropylene, polycarbonate, polyamide and so on.

After step ST104, a conventional lubricant is applied, as shown by stepST105 in FIG. 1. In this step, lubricant is applied to the magnetic disk1 by immersing the magnetic disk 1 in a lubricant solution and thenpulling out the magnetic disk 1 at a predetermined speed.

Once step ST105 has been performed, tape burnishing is repeated in stepST106. The same procedure is used as in step ST104, though a differentamount of pressure is applied. That is, in FIG. 8, 40 kPa is applied topress the lapping tape 56 against the magnetic disk 1.

As described above, tape burnishing is performed before and after theformation of the lubricant. During the latter tape burnishing process,the amount of pressure applied onto the magnetic disk 1 by the lappingtape 56 is reduced, thereby ensuring that foreign matter present on thesurface of the magnetic disk 1 after the formation of the lubricantlayer can be removed.

It has been found by experimentation that when a magnetic disk 1 isconditioned using the above steps, a magnetic disk 1 can be produced ina favorable state for subsequent magnetic transfer, with no foreignmatter or unwanted protrusions present on the surface of the magneticdisk 1 before magnetic transfer is performed. This is described indetail later in this specification with reference to FIG. 13.

The following describes steps ST107 and ST108 with reference to FIG. 9.In FIG. 9, numeral 60 indicates a clean booth. To stop particles offoreign matter from entering the clean booth 60, a filter 61 with acollection efficiency of 99.9999995% for particles of foreign matterthat are 0.01 microns or larger in size is provided at the top of theclean booth 60. Apparatuses for performing step ST107, in which thepresence of foreign matter on the surface of the magnetic disk 1 isinvestigated using an optical detection method, and step ST108, in whichmagnetic transfer is performed, are arranged in the clean booth 60.

First, a loading cassette 62 into which a magnetic disk 1 that has beenprocessed as far as step ST106 (tape burnishing) is brought into theclean booth 60 from the left side of the clean booth 60, in thedirection shown by the arrow I.

Next, the cleaning robot 69 retrieves the magnetic disk 1 from thecassette 62 and places the magnetic disk 1 onto a spindle 64. In FIG. 9,numeral 65 indicates a laser source, numeral 66 indicates a detector,and number 67 indicates a cover that prevents laser light from escapingto the periphery. Laser light emitted by the laser source 65 isirradiated on the magnetic disk 1 as the magnetic disk 1 is rotated bythe spindle 64, and the resulting scattered light is detected by thedetector 66. By doing so, the presence of foreign matter on the surfaceof the magnetic disk 1 can be investigated, at least before magnetictransfer is performed.

If the detector 66 finds that foreign matter is present, the magneticdisk 1 is placed into an “NG” cassette (not illustrated) by a cleaningrobot 70.

If the detector 66 finds that no foreign matter is present on thesurface of the magnetic disk 1, then the cleaning robot 70 places themagnetic disk 1 on the support 6 to carry out the magnetic transfer step108.

As used in the present embodiment, it is preferable to use a scatteredlight method to investigate the surface of the magnetic disk 1 in stepST107. This is because investigation using scattered light is suited tothe detection of foreign matter on the surface of a disk, and byperforming such investigation immediately before the magnetic transferprocess, the magnetic transfer process can be restricted to magneticdisks 1 on which foreign matter is not present, making the process moreefficient.

The magnetic transfer process shown as step ST108 is performed next.This process is described in detail below with reference to FIGS. 10 and11. FIGS. 10 and 11 are cross-sectional drawings showing the apparatusthat performs step ST108 and the operation of this apparatus. FIG. 10shows the apparatus with the magnetic transfer master 2 and the magneticdisk 1 being separated, while FIG. 11 shows the apparatus with themagnetic transfer master 2 and the magnetic disk 1 being pressedtogether.

This apparatus has a configuration similar to that of the apparatus usedin step ST102 as shown in FIGS. 3 and 4. Accordingly, identicalcomponents are referred to using the same reference numerals. The maindifferences between the apparatuses are that the magnetic disk 1 ismounted on the apparatus in place of the cleaning NiP disk 1A in FIGS. 3and 4, and, as shown in FIG. 11, this apparatus also includes a magnet20. The contact surface 3 of the magnetic transfer master 2 that comesinto contact with the magnetic disk 1 is as shown in FIG. 5. Themagnetic transfer master 2 is held on the holding arm 14 by air that issucked through a through hole (not illustrated) provided in the holdingarm 14.

First, the separating operation is described with reference to FIG. 10.The air supplying pump 12 is operated with the exhaust valve 11 closedand the air supplying valve 13 open, so that air flows into the air duct8. As a result, air is pumped through the through hole 7 upward, in thedirection shown by the arrow A in FIG. 10. The air that is pumpedthrough the through hole 7 presses the boss 5 upward. The air is alsopumped into the grooves 4, as shown by the arrows B. This air that ispumped into the grooves 4 spreads out radially from the center of themagnetic transfer master 2 via the grooves 4. The air then passesthrough the gap between the magnetic transfer master 2 and the magneticdisk 1 and escapes to the atmosphere. The relationship between thepassage of time and the air pressure of the air in the gap (hereafterreferred to as “gap S”) between the magnetic transfer master 2 and themagnetic disk 1 is shown in FIG. 7.

The pressing is described next with reference to FIG. 11. During thisoperation, the air supplying pump 12 is stopped and the air supplyingvalve 13 is closed. As a result, the magnetic transfer master 2 movesdownward due to gravity, and the boss 5 engages the center hole of themagnetic disk 1, thereby mounting the magnetic disk 1. After this, theexhaust valve 11 is opened and the suction pump 10 is operated. As aresult, air flows through the through hole 7 downwards, in the directionshown by the arrow C in FIG. 11. The air in the grooves 4 also flowsthrough a gap 51 between the center hole of the magnetic disk 1 and theboss 5, resulting in the air pressure in the grooves 4 that are coveredby the magnetic disk 1 falling below atmospheric pressure. Therefore,the magnetic disk 1 is pressed onto the magnetic transfer master 2mainly by atmospheric pressure 15. In FIG. 7, the period that followsthe start of evacuation at zero seconds and during which the airpressure in the gap S is about 30 kPa corresponds to the time when thedisks are pressed together.

After this, the magnet 20 is moved in the direction shown by the arrow Dand so approaches the magnetic transfer master 2. This movement in thedirection D is stopped when the magnet 20 is 1 mm from the magnetictransfer master 2. Next the magnet 20 is moved at least once around thecircumference of the magnetic disk 1, which is to say in the directionshown by the arrow E, thereby applying the magnetic field required fortransfer. By using this method, the pattern formed in the magnetic film30 formed on the surface of the magnetic transfer master 2 is formed onthe surface of the magnetic disk 1.

Once the magnetic transfer of step ST108 has been completed, a cleanrobot 71 loads the magnetic disk 1 into a discharge cassette 63, beforethe discharge cassette 63 is discharged from the clean booth 60, asshown in FIG. 9.

In the present embodiment, the investigation in step ST107 and themagnetic transfer in step ST108 are performed together in the cleanbooth 60. Since the magnetic transfer in step ST108 is performedimmediately after the investigation of the surface of the magnetic disk1 in step ST107, no foreign matter gathers on the surface of themagnetic disk 1 between the two steps. This stops depressions fromforming in the surface of the magnetic disk 1 during the magnetictransfer process.

It should be noted that in the present embodiment, the magnetic disk 1is transported in steps ST107 and ST108 with its recording surfacefacing upward, although as one example it is also possible to set thesurface of the magnetic disk in a vertical orientation where it isparallel to the flow of air from the filter 61 in the clean booth 60(vertical flow in FIG. 9). In this case, the flow of foreign matterconveyed by the air flow becomes parallel to the surface of the magneticdisk, so that it becomes more difficult for foreign matter to gather onthe surface of the magnetic disk.

Also, in the present embodiment, the spindle 64 and the support 6 arearranged separately, although a configuration that allows steps ST107and ST108 to be performed at the same position may be used.

The following describes the “glide height test” performed as step ST109,with reference to FIG. 12. A glide height test is a test where adetection head scans above the magnetic disk, and defects in themagnetic disk are detected by detecting an impact due to collisionsbetween the detection head and the protrusion on the magnetic disk. Whenperforming this test, the clearance between the detection head and themagnetic disk is set slightly smaller than the clearance used when amagnetic head scans the magnetic disk.

FIG. 12 is a perspective drawing showing an apparatus for performing theglide height test in the present embodiment of the present invention.This apparatus includes a spindle 21 for supporting and rotating themagnetic disk 1 that has been subjected to magnetic transfer in stepST108. The magnetic disk 1 is attached to the spindle 21 by a clampmechanism 22. A glide height test head slider 40 is supported by a headsupporting mechanism 23. This head supporting mechanism 23 is supportedat its base by a guide arm 24 in the form of a cantilever. An acousticemission sensor 25 is attached to this guide arm 24. A head positioningunit 26 acts on the head supporting mechanism 23 and the guide arm 24 tomove and position the head 40 above the recording surface of themagnetic disk 1. The operation of the head positioning unit 26 iscontrolled by a positioning control unit 27. The operation of thespindle 21 is control by a spindle control unit 28. The positioningcontrol unit 27 and spindle control unit 28 are controlled by acontroller 29.

The following describes the operation of the above apparatus. First, thecontroller 29 lets the spindle control unit 28 rotate the magnetic disk1 at a predetermined speed. Next, the positioning control unit 27 letsthe head positioning unit 26 move in the direction shown by the arrow Fin FIG. 12 and stop when there is a predetermined distance, for example,15 nm, between the head 40 and the magnetic disk 1. This position is setaccording to the following method.

When the head positioning unit 26 has been moved to a certain position,the distance between the magnetic disk 1 and the head 40 is measured.The distance by which the head positioning unit 26 needs to move untilthe distance between the head 40 and the magnetic disk 1 is 15 nm isthen calculated and stored by the controller 29. The controller 29 letsthe positioning control unit 27 move the head positioning unit 26 and sosets the distance between the head 40 and the magnetic disk 1 at 15 nm.The distance left between the head 40 and the magnetic disk 1, which isto say 15 nm, is set as described above at a value that is equal to orlower than the distance a magnetic head, provided in arecording/reproducing apparatus into which the magnetic disk 1 has beenloaded, floats above the magnetic disk 1 during recording andreproduction.

Next, while the magnetic disk 1 is being rotated, the head 40 iscontrolled by the positioning control unit 27 so as to move in thedirection G shown in FIG. 12, which is to say in the radial direction ofthe magnetic disk 1, to perform a glide height test for the surface ofthe magnetic disk 1 that came into contact with the magnetic transfermaster 2 during the magnetic transfer in step ST108.

The presence of unwanted protrusions on the surface of the magnetic disk1, and in particular protrusions that are at least as high as theclearance between the magnetic disk 1 and a magnetic head duringrecording and reproduction, are detected by the acoustic emission sensor25, based on excessive vibrational energy produced due to collisions.

Here, when one or more unwanted protrusions are found on a magnetic disk1, the disk is judged to be defective, and the procedure returns, asshown in FIG. 1, to step ST102 where the cleaning of the magnetictransfer master 2 begins.

When no unwanted protrusions are detected, the disk is judged to benormal, and the following step, step ST110, is performed. In step ST110,the presence of defects on the surface of the magnetic disk 1, and inparticular on the surface of the magnetic disk 1 that came into contactwith the magnetic transfer master 2 during the magnetic transfer in stepST108, is investigated. The same method as step ST107 in FIG. 1 is used,so that the defects in the surfaces of the magnetic disk 1 are detectedoptically.

When defects are found by this step, the procedure returns to step ST102where the cleaning of the magnetic transfer master 2 begins, as shown inFIG. 1. When no defects are found, the magnetic disk 1 is installed in ahard disk apparatus.

By performing the above steps, highly reliable magnetic transfer can beperformed. No defects are left on the magnetic disk after magnetictransfer and signal deterioration is avoided.

This is described below with reference to FIG. 13. The table of FIG. 13shows the results of measurements in which the number of defects onmagnetic disks were measured using a commercial optical detection methodand the results of an investigation into signal errors as well, withrespect to magnetic disks produced according to a variety of magnetictransfer methods, including the magnetic transfer method of the presentinvention.

Sample methods 1 to 8 are shown on different rows, with the processesincluded in each method being shown in order from left to right.

The number of defects given as part of the evaluation results shows anaverage of the number of defects calculated as a relative value wherethe number of defects on a standard disk that has not been subjected tomagnetic transfer is set as one.

Signal errors are shown in the D.O. column in the evaluation results.The signals recorded by magnetic transfer were reproduced and evaluated,a comparison was made with the signal output achieved when reading orwriting a standard magnetic disk that has not been subjected to magnetictransfer, and a relative evaluation was made based on the number ofdefects where dropouts occurred. The results of the evaluation wereexpressed as ranks “A”, “B” and “C”. The rank A means that dropouts weresimilar to those in the signal output achieved when reading or writing astandard magnetic disk that has not been subjected to magnetic transfer.The rank B means that dropouts were 1.5 times those in the signal outputachieved from the standard magnetic disk. The rank C means that dropoutswere above 1.5 times those in the signal output achieved from thestandard magnetic disk. None of the sample method was ranked C.

In the experiments for evaluating the disks, magnetic transfer wasperformed in accordance with FIGS. 10 and 11 of the present embodiment.For sample methods 6, 7, and 8, an optical detection using a scatteredlight method was performed before the magnetic transfer, and magnetictransfer was performed only for magnetic disks for which no defects weredetected. The optical detection apparatus and magnetic transferapparatus were provided as one device, as shown in FIG. 9 of the presentembodiment, with the magnetic transfer being performed immediately afterthe optical detection. In the optical detection, foreign matter wasdetected on the surfaces of 5% of the disks processed using samplemethod 6, 0% of the disks processed using sample method 7, and 0% of thedisks processed using sample method 8.

The experiments were performed with the magnetic transfer master 2having been subjected to step ST101 (washing the magnetic transfermaster disk) and step ST102 (pressing and separating of the magnetictransfer master disk and a cleaning disk), so that no fine particles offoreign matter or unwanted protrusions were present on the contactsurface 3.

As can be clearly seen from the results for sample method 6, samplemethod 7, and sample method 8 in FIG. 13, performing an opticaldetection on magnetic disks immediately before magnetic transfer enablesmagnetic disks that meet the same standard, in terms of both the numberof defects in the disk surface after magnetic transfer and signalerrors, as a conventional disk on which magnetic transfer has not beenperformed. It is clear from the results for the other sample methodsthat when optical detection is not performed on magnetic disksimmediately before magnetic transfer, both the number of defects in themagnetic disk surface and signal errors are worse than for aconventional magnetic disk.

These results show that when foreign matter is present on the surface ofthe magnetic disk immediately before magnetic transfer is performed,magnetic transfer causes depressions to be performed in the surface ofthe magnetic disk. As shown by sample method 1, sample method 4, andsample method 5, once there are depressions in the magnetic disk, whileit is possible to repair the defects in the surface of the magnetic diskto a certain degree by performing tape burnishing, it is difficult torepair the disk sufficiently for signal errors to be significantlyprevented. The reason for this is that although the rises in the disksurface near the depressions can be removed by tape burnishing, tapeburnishing does not flatten out the depressions, so that spacing occursduring reproduction, resulting in lowered signal output that appears assignal errors.

When, as part of a glide height test, head burnishing, or the like, ahead scans across the surface of a magnetic disk before magnetictransfer is performed, it becomes easier for foreign matter to gather onthe surface of the magnetic disk. When a head scans across the surfaceof a magnetic disk, the head is moved to a predetermined position, suchas 15 nm from the magnetic disk. At such times, it is impossible to stopthe head from coming into physical contact with the magnetic disk whilethe head is being stabilized at the desired distance from the disk. Whencollisions occur between the head and the magnetic disk, the resultingabrasion damages the surface of the magnetic disk and fragments of diskend up on the disk surface. This problem is becoming increasinglyserious as the floating height is decreased to assist in the achievementof higher recording densities. As a result, it is better not to scan ahead above the surface of a magnetic disk before magnetic transfer.

In FIG. 13, sample method 1, sample method 2, sample method 3, andsample method 6 represent methods where a head scans above the surfaceof a magnetic disk before magnetic transfer, while sample method 4,sample method 5, sample method 7, and sample method 8 represent methodswhere a head does not scan above the surface of a magnetic disk beforemagnetic transfer.

As can be seen from the evaluation results in FIG. 13, in sample method1 a head scans above the surface of a magnetic disk before magnetictransfer, and while the resulting defects are repaired to a certainextent by the tape burnishing performed after the magnetic transfer,this is not sufficient to stop signal errors from occurring. On theother hand, in sample method 6 favorable results are obtained in spiteof a head scanning the surface of the magnetic disk before magnetictransfer is performed. This is because defects are detected by theoptical detection performed before the magnetic transfer. While theoccurrence of defects was 0% for both sample methods 7 and 8, theoccurrence of defects for sample method 6 was 5%.

From the above, it can be seen that sample method 7 and sample method 8of the present embodiment are preferable as methods for conditioningmagnetic disks to be subjected to magnetic transfer. In sample method 7,tape burnishing is performed after magnetic transfer, though similarevaluation results were obtained for sample method 8 where this processwas omitted. Accordingly, the tape burnishing process performed afterthe magnetic transfer may be omitted.

With the present embodiment described above, magnetic transfer isperformed after sputtering, tape burnishing, application of lubricant,and a second tape burnishing, so that the magnetic transfer can beperformed with high reliability.

In the present embodiment, the surface of the magnetic disk is measuredusing an optical detection method immediately before magnetic transferis performed, and the magnetic transfer is performed immediately afterit has been confirmed that there are no defects in the surface of themagnetic disk. As a result, it is possible to perform highly reliablemagnetic transfer that does not create depressions in the surface of themagnetic disk.

In the present embodiment, head scanning processes such as headburnishing or a glide height test are not performed before the magnetictransfer, so that it is possible to perform highly reliable magnetictransfer that does not create depressions in the surface of the magneticdisk.

It should be noted that the joint optical detection in step ST107 andmagnetic transfer in step ST108 is not limited to arranging theequipment for performing these processes in the same clean booth, asdescribed above in the present embodiment. As examples, the same effectcan be achieved if two clean booths are connected to combine theprocesses, or if the equipment itself is combined into one deviceprovided in a highly dustproof clean booth.

Also, the present embodiment uses a configuration where, as shown inFIG. 9, the surface of the magnetic disk is arranged horizontally,although the disk surface may be held vertically so as to make it moredifficult for foreign matter to gather on the disk. In this case, whenmagnetic transfer is performed in step ST108, the configuration thatuses gravity, such as that of the present embodiment shown in FIG. 11,is not used as a means for urging the magnetic transfer master 2 towardthe magnetic disk 1. Instead, a configuration where the magnetictransfer master 2 is urged toward the magnetic disk 1, for example, withan energizing spring provided between the holding arm 14 and the holdingmount 16 may be used. In this way, the same effects can be achieved.

Second Embodiment

The following describes, with reference to FIGS. 14 through 17, amagnetic transfer apparatus and a method for a magnetic transferaccording to the second embodiment of the present invention.

FIG. 14 shows the flow of the procedure that performs magnetic transferin the present embodiment. The magnetic transfer master used here hasthe same configuration as the magnetic transfer master 2 of the firstembodiment that is shown in FIGS. 2 and 5. As shown in step ST201 inFIG. 14, the magnetic transfer master 2 is first washed using aconventional method, such as scrubbing. However, when an existingwashing method is used, it has been found that it is not possible toremove minute particles, whose sizes range from about 20 to 50 nm, offoreign matter that remains on the contact surface 3 of the magnetictransfer master 2. For this reason, step ST202 is performed to removesuch minute particles of foreign matter completely. Step ST202 issimilar to step ST102 that was described in the first embodiment. StepST202 is described below with reference to FIGS. 15 and 16.

FIGS. 15 and 16 are cross-sectional drawings showing the apparatus thatperforms step ST202 and the operation of this apparatus. FIG. 15 showsthe apparatus during the separation operation, while FIG. 16 shows theapparatus during the pressing operation. With the exception of a holdingarm 17, the configuration and operation of this apparatus are the sameas that for the apparatus used in the first embodiment that is shown inFIGS. 3 and 4. Accordingly, components that are the same as theapparatus described earlier have been given the same reference numeralsand are not described in detail. The holding arm 17 has an internalthrough hole (not illustrated) through which air is drawn so as toattach the magnetic transfer master 2 onto the holding arm 17 throughsuction. In this way, the holding arm 17 holds the magnetic transfermaster 2.

First, the separation operation shown in FIG. 15 is performed. Thisoperation is very similar to the operation that was described earlierwith reference to FIG. 3. The magnetic transfer master 2 is held by theholding arm 17. The air supplying pump 12 is operated with the exhaustvalve 11 closed and the air supplying valve 13 open, so that air flowsthrough the air duct 8 and the through hole 7 and is pumped into thegrooves 4. This air that is pumped into the grooves 4 spreads outradially from the center of the magnetic transfer master 2, passesthrough the gap between the magnetic transfer master 2 and the cleaningNiP disk 1A, and escapes to the atmosphere. This flow of air carries anyminute particles of foreign matter that adhere to the surface of themagnetic transfer master 2 or the cleaning NiP disk 1A, exhausting theminto the atmosphere together with the air.

The relationship between the passage of time and the air pressure of theair in the gap S between the magnetic transfer master 2 and the cleaningNiP disk 1A is as shown in FIG. 7.

Then, the separation operation shown in FIG. 16 is performed. Thisoperation is very similar to the operation that was described earlierwith reference to FIG. 4. During this separation operation, the airsupplying pump 12 is stopped and the air supplying valve 13 is closed.As a result, since the suction that held the magnetic transfer master 2onto the holding arm 17 is removed, the magnetic transfer master 2 isseparated from the holding arm 17. The magnetic transfer master 2 fallsdue to gravity, so that the boss 5 engages the center hole of thecleaning NiP disk 1A, thereby mounting the cleaning NiP disk 1A.

After this, the exhaust valve 11 is opened and the suction pump 10 isoperated. The air in the grooves 4 flows through the gap between thecenter hole of the cleaning NiP disk 1A and the boss 5 and out via thethrough hole 7, so that the cleaning NiP disk 1A is pressed onto themagnetic transfer master 2 mainly by atmospheric pressure 15. As aresult, foreign matter present on the magnetic transfer master 2 issandwiched between the cleaning NiP disk 1A and the magnetic transfermaster 2. Since the cleaning NiP disk 1A is manufactured using a softermaterial than the magnetic transfer master 2, foreign matter that issandwiched between the two disks sinks into the cleaning NiP disk 1A orcauses depressions in the cleaning NiP disk 1A, without damaging themagnetic transfer master 2. Unintended minute protrusions in themagnetic transfer master 2 are also flattened when the magnetic transfermaster 2 is pressed against the cleaning NiP disk 1A.

Next, the separation operation shown in FIG. 15 is performed again. Thatis to say, the exhaust valve 11 is closed, the air supplying valve 13 isopened, and the air supplying pump 12 is operated. This results in airbeing pumped in the directions shown by the arrows A and B in FIG. 15.The air pumped in this way forces the magnetic transfer master 2 upwarduntil the magnetic transfer master 2 is stopped by abutting against theholding arm 17. At this point, air passes through the grooves 4 as shownby the arrows B, and so is continually pumped radially outwards from thecenter of the magnetic transfer master 2 to the outer periphery of thedisk. As a result, foreign matter that is present on the surface of themagnetic transfer master 2 is expelled to the atmosphere together withthe pumped air from the air supplying pump 12, or is transferred ontothe cleaning NiP disk 1A. By repeating the pressing and separatingoperations a predetermined number of times, foreign matter can beremoved from the surface of the magnetic transfer master 2.

In step ST202, it is preferable that the cleaning disk is not coatedwith a lubricant. If, as with a conventional magnetic disk, lubricant isapplied, the ability of the cleaning disk to absorb foreign matter isreduced, so that it becomes more difficult for foreign matter to adhereto the cleaning disk. By using a cleaning NiP disk onto which lubricanthas not been applied, it can be ensured that foreign matter present onthe magnetic transfer master will adhere to the cleaning disk.

As mentioned earlier, it is preferable that the cleaning NiP disk 1A issofter than the magnetic transfer master 2. If the surface hardness ofthe cleaning NiP disk 1A is higher than that of the magnetic transfermaster 2, the following problem occurs. When foreign matter that isharder than the magnetic transfer master 2 but softer than the cleaningNiP disk 1A is present between the cleaning NiP disk 1A and the magnetictransfer master 2, such foreign matter does not sink into the surface ofthe cleaning NiP disk 1A since it is harder than the surface of thecleaning NiP disk 1A. Instead, the foreign matter sinks into the surfaceof the magnetic transfer master 2 which is softer than the foreignmatter, thereby causing defects in the magnetic transfer master 2. Suchdefects, once caused in the magnetic transfer master 2, adversely affectall of the subsequent magnetic transfer processes.

The cleaning disk can be made by plating an aluminum substrate with aNiP layer. It is also possible to form a plating layer with magneticcharacteristics, such as a layer of Co—Re—P, Co—Ni—P, or Co—Ni—Re—P.When a plating layer with magnetic characteristics is formed, thefollowing effect is achieved. When unwanted protrusions are present inthe magnetic film present on the surface of the magnetic transfer master2, there are cases where the repeating pressing and separatingoperations peel off some of the magnetic film. However, when there is aplating layer with magnetic characteristics on the surface of thecleaning NiP disk 1A, the pieces of magnetic film that peel offinvariably adhere to the cleaning disk.

It is preferable that a region Sa where there is contact between thecleaning NiP disk 1A and the magnetic transfer master 2 is bigger than aregion Sb where there is contact between the magnetic disk 1 and themagnetic transfer master 2 and that the region Sa includes all of theregion Sb. This is because if the magnetic disk 1 contacts the magnetictransfer master 2 in a position beyond the region Sa where cleaning isperformed, there is the risk of foreign matter adhering to the magneticdisk 1.

One method of making the region Sa bigger than the region Sb is to use adisk that is larger than the magnetic disk 1 as the cleaning NiP disk1A. However, in practice there are cases where the cleaning NiP disk 1Aand the magnetic disk 1 are manufactured by the same manufacturingapparatus. In such cases, both disks are the same size, so that thefollowing method is used to make the region Sa larger than the regionSb. The cleaning NiP disk 1A is placed off-center on the support 6 inFIG. 15, and is rotated every time one cycle of the pressing andseparating operations is performed. As a result, the position of thecleaning NiP disk 1A relative to the magnetic transfer master 2progressively changes, so that the suction and pumping are applied to anarea wider than region Sb.

Following step ST202 in FIG. 14, an investigation is performed to detectwhether any foreign matter is adhering to surface 3 of the magnetictransfer master 2. Here, it is extremely difficult to directly detectforeign matter adhering to the surface 3 of the magnetic transfer master2. This is because there are minute recesses and protrusions in theheight of the surface 3 of the magnetic transfer master 2 due to thepresence of the grooves 4 and minute recesses and protrusions in themagnetic film 30, as shown in FIG. 2. If, for example, an opticaldetection method is used, light is scattered at the edges of suchrecesses and protrusions, and foreign matter is mistakenly judged to bepresent at such positions.

With the present embodiment, the presence of foreign matter on thesurface 3 of the magnetic transfer master 2 can be simply and reliablyinvestigated using the following method. Instead of performing a directinvestigation of the surface of the magnetic transfer master 2, themagnetic transfer master 2 is pressed against a detection NiP disk andthe condition of the surface 3 of the magnetic transfer master 2 isdetected from the imprint in the surface of the detection NiP disk. Thismethod of investigating the surface 3 of the magnetic transfer master 2is described in detail below.

First, as shown by step ST203 in FIG. 14, the magnetic transfer master 2is pressed against and separated from a detection NiP disk 1B once only.This can be performed by a similar apparatus to the apparatus used inST202 and shown in FIGS. 15 and 16. The difference to step ST202 is thatthe detection NiP disk 1B is used in place of the cleaning NiP disk 1A.The surface material of the detection NiP disk 1B is softer than thesurface of the magnetic transfer master 2. As a result, recesses andprotrusions in the surface of the magnetic transfer master 2 aretransferred onto the surface of the detection NiP disk 1B.

Next, in step ST204, an optical investigation is performed for thesurface of the detection NiP disk 1B that was pressed against themagnetic transfer master 2. This optical investigation can be conductedby using the Doppler effect to measure the profile of the disk, that is,the defects, to see whether there are any defects with a depth that isequal to or greater than a predetermined depth.

The recesses and protrusions in the surface of the magnetic transfermaster 2 have been transferred onto the detection NiP disk 1B, whosesurface is flush and that does not include grooves like the magnetictransfer master 2. As a result, the scattering of light does not occurduring optical measurement, so that the investigation can be performedproperly. By performing this investigation, the magnetic transfer master2 can be investigated indirectly.

When no defects with a depth equal to or greater than the predetermineddepth are found in the investigation in step ST204, it is judged that noforeign matter is present on the magnetic transfer master 2. Using thismethod, a reliable judgment as to whether foreign matter is present onthe magnetic transfer master 2 can be made using a simple procedure.

When no defects with a depth equal to or greater than the predetermineddepth are found in the investigation in step ST204, the magnetictransfer master 2 that was used in step ST203 is used for the magnetictransfer performed in step ST208.

When the magnetic transfer master 2 is found to be defective in theinvestigation in step ST204, the magnetic transfer master 2 is subjectedto cleaning again in step ST202.

As shown by steps ST205 and ST206, the cleaning NiP disk 1A anddetection NiP disk 1B are optically investigated before being used inthe cleaning and investigation of the magnetic transfer master 2. Here,a scattered light method is preferably used as the method for opticallyinvestigating the disks. This is because when a scattered light methodis used, it is especially easy to detect foreign matter on the surfaceof a disk. The following describes, with reference to FIG. 17, why it ispreferable to perform an optical investigation of the disk beforecleaning.

FIG. 17 is a graph showing the following data. First, an opticalinvestigation was performed for a number of cleaning NiP disks 1A andthe disks were classified into disks on whose surfaces foreign matterwas found and disks on whose surfaces no foreign matter was found. Next,each cleaning NiP disk 1A was repeatedly pressed against and separatedfrom a magnetic transfer master 2, with the number of defects in thesurface of the cleaning NiP disk 1A being counted after each cycle. Therelationship between the number of times the pressing operation wasperformed and the number of defects in the surface of each cleaning NiPdisk 1A is shown in the graph in FIG. 17. In FIG. 17, the blacktriangles show data for disks that were found to have foreign matter ontheir surfaces, while the black squares show disks that were found tohave no foreign matter on their surfaces.

In the above experiment, after the cleaning NiP disk 1A and the magnetictransfer master 2 were pressed together and separated once, an opticalinvestigation was performed for the surface of the cleaning NiP disk 1A,and the number of defects in the surface was counted. This measurementwas made using a disk tester 4218 made by THOT. The number of defectsfound at this point was taken as an initial value. Since the defects onthe magnetic transfer master 2 are transferred onto the cleaning NiPdisk 1A at this point, investigating the surface of the cleaning NiPdisk 1A makes it possible to ascertain the state of the defects in themagnetic transfer master 2 indirectly.

Next, after the cleaning NiP disk 1A and magnetic transfer master 2 havebeen pressed together and separated a predetermined number of times, thecleaning NiP disk 1A is replaced with a new cleaning NiP disk 1A. Afterthis new cleaning NiP disk 1A and the magnetic transfer master 2 havebeen pressed together and separated once, an optical investigation isperformed for the surface of the new cleaning NiP disk 1A and the numberof defects is counted. This number of defects can be regarded as anindirect indication of the number of defects on the magnetic transfermaster 2.

From the results shown in FIG. 17, it can be seen that when a cleaningNiP disk 1A with no foreign matter is used, the number of defects on themagnetic transfer master 2 is reduced to zero when pressing andseparating is performed ten times. On the other hand, when a cleaningNiP disk with foreign matter is used, pressing and separating need to beperformed over one thousand times to reduce the number of defects on themagnetic transfer master 2 to zero.

This is to say, the cleaning process performed for the magnetic transfermaster 2 (step ST202 in FIG. 14) can be performed efficiently if aninvestigation is first performed for cleaning NiP disks and onlycleaning NiP disks that do not have foreign matter are used for thecleaning.

The reason an investigation is performed, as shown by step ST206, forthe detection NiP disk 1B before the disk is pressed onto the magnetictransfer master 2 is that this prevents, from the start, foreign matterfrom adhering to the magnetic transfer master 2 due to contact with thedetection NiP disk 1B.

The following describes a method for manufacturing and conditioning themagnetic disk 1. First, a magnetic layer is formed on the surface of asubstrate using a conventional method. As one example, this magneticlayer can be formed by performing a dry plating method, such as vapordeposition or sputtering, on an aluminum substrate. Conventionally, thismagnetic layer is protected by forming a protective layer on top of themagnetic layer using dip coating, spin coating, or a dry plating method,such as vapor deposition or sputtering.

Next, a lubricant layer is formed using a conventional method. Thislubricant is applied to the magnetic disk by immersing the magnetic disk1 disk in a lubricant solution and then pulling out the disk at apredetermined speed. In this way, the magnetic disk 1 is conditioned.

Next, as shown by step ST207, the magnetic disk 1 is subjected to anoptical investigation to detect whether foreign matter is present on thesurface of the magnetic disk 1. Here, it is preferable to use ascattered light detection method for the investigation, since ascattered light detection method is suited to detecting foreign matteron the surface of a disk. In order to remove definitely any foreignmatter immediately before the magnetic transfer that follows thisinvestigation, this method preferably should be used. Naturally, it isalso possible to take an existing magnetic disk 1 and subject it to theoptical investigation in step ST207. When no particles with a particlesize that is equal to or greater than a predetermined size are presenton the surface of a magnetic disk 1, the magnetic disk 1 is supplied tostep ST208 where magnetic transfer is performed.

The following describes step ST208 in which magnetic transfer isperformed. The apparatus for performing this process is similar to theapparatus that was used in the first embodiment and is shown in FIGS. 10and 11, so that this apparatus is described below with reference toFIGS. 10 and 11.

In the magnetic transfer of step ST208, the separating operation forseparating the magnetic disk 1 and the magnetic transfer master 2 is asshown in FIG. 10. The relationship between the passage of time and theair pressure of the air in the gap S between the magnetic transfermaster 2 and the magnetic disk 1 during this operation is as shown inFIG. 7.

The pressing operation is achieved using suction and is performed asshown in FIG. 11. During this operation, the air supplying pump 12 isstopped and the air supplying valve 13 is closed. As a result, theholding arm 14 to which the magnetic transfer master 2 is attached movesdownward due to its own weight, and the boss 5 engages the center holeof the magnetic disk 1, thereby mounting the magnetic disk 1. Afterthis, the exhaust valve 11 is opened and the suction pump 10 isoperated. As a result, air flows through the through hole 7 downwards,which is to say, in the direction shown by the arrow C in FIG. 11. Theair in the grooves 4, which is to say the air in the gap S, also flowsthrough a gap between the center hole of the magnetic disk 1 and theboss 5.

As a result, the entire surfaces of the magnetic disk 1 and the magnetictransfer master 2 are pressed together, and the pressure becomes lowerthan atmospheric pressure, so that the magnetic disk 1 is pressed ontothe magnetic transfer master 2 by the atmospheric pressure 15.

Next, as shown in FIG. 11, the magnet 20 is moved in the direction shownby the arrow D and so approaches the magnetic transfer master 2. Whenthe magnet 20 is 1 mm from the magnetic transfer master 2, the movementin the direction D is stopped. Next, the magnet 20 is moved at leastonce around the circumference of the magnetic disk 1, in the directionshown by the arrow E, thereby applying the magnetic field required fortransfer.

After this, the separation process shown in FIG. 10 is repeated toseparate the magnetic transfer master 2 and the magnetic disk 1 fromanother.

Next, a glide height test is performed as step ST209. This process issimilar to the glide height test performed in step ST109 in the firstembodiment, and is performed using the apparatus shown in FIG. 12.

In step ST209, when one or more unwanted protrusions are found on amagnetic disk 1, the disk is judged to be defective, and the procedurereturns to step ST202 in FIG. 14, where the cleaning of the magnetictransfer master 2 begins. When no unwanted protrusions are detected, thedisk is judged to be normal, and the following step ST210, is performed.

In step ST210, the presence of defects on the surface of the magneticdisk 1 is investigated using an optical detection method. When defectsare found by this step, the procedure returns to step ST202 where thecleaning of the magnetic transfer master 2 begins, as shown in FIG. 14.When no defects are found, the magnetic disk 1 is installed in a harddisk apparatus.

As described above, while magnetic transfer is being repeatedlyperformed, it is judged whether foreign matter is adhering to themagnetic transfer master 2 using the following method. An investigationis performed to detect defects in the surface of the magnetic disk 1after the magnetic disk 1 has been subjected to magnetic transfer, themagnetic transfer master 2 is cleaned when defects are found, and thenanother investigation is performed. By doing so, the foreign matter onthe magnetic transfer master 2 can be quickly and easily detected, andremoved. This makes highly reliable magnetic transfer possible.

With the present embodiment, a disk whose surface has been subjected tooptical detection to confirm that it does not have foreign matter ispressed against and separated from a magnetic transfer master disk toclean the magnetic transfer master disk. In this way the magnetictransfer master disk can be completely cleaned in an efficient manner.

Also with the present embodiment, the judgment as to whether foreignmatter has been removed from the surface of the magnetic transfer masterdisk is made for the magnetic transfer master disk after the pressingoperation. This simplifies the extent to which the master disk iswashed, and makes a correct judgment possible.

It should be noted that while the magnetic transfer master 2 issubjected to step ST202 after washing in the present embodiment, themagnetic transfer master 2 still can be cleaned sufficiently if stepST201 is omitted and the processing instead starts from step ST202.

Also, the same apparatus may be used for steps ST202 and ST208.

The magnetic disk 1 and the magnetic transfer master 2 do not need to bealigned using the boss 5, as described above. A movable stage may beprovided on the holding arm 14 that holds the magnetic transfer master 2and an optical method may be used to align the magnetic disk 1 and themagnetic transfer master 2.

INDUSTRIAL APPLICABILITY

The present invention achieves a highly reliable magnetic transfermethod that does not create minute protrusions on a magnetic disk whentransferring a magnetic pattern corresponding to an information signalonto the magnetic disk using a magnetic transfer master disk. Theinvention also achieves a magnetic transfer method where a magnetictransfer master disk is efficiently and reliably cleaned, making theconditioning process highly efficient.

1. A method of manufacturing a master-information-recorded magneticdisk, comprising: a first step of preparing a magnetic disk; a secondstep of forming a layer of lubricant on the magnetic disk; a third stepof bringing the magnetic disk into close contact with a magnetictransfer master having a magnetic film formed on at least one side andmagnetically transferring a pattern of the magnetic film on the magnetictransfer master onto the magnetic disk through application of anexternal magnetic field; and a fourth step of burnishing at least asurface of the magnetic disk that comes into contact with the magnetictransfer master, wherein the first step, the fourth step, the secondstep, the fourth step, and the third step are performed in the statedorder.
 2. The method of manufacturing a master-information-recordedmagnetic disk according to claim 1, wherein an amount of pressureapplied by a lapping material onto the magnetic disk in a burnishingprocess in the fourth step performed after the first step is higher thanan amount of pressure applied in a burnishing process performed afterthe second step.
 3. The method of manufacturing amaster-information-recorded magnetic disk according to claim 1, furthercomprising a fifth step of detecting defects in the magnetic disk byscanning the magnetic disk with a detection head that floats apredetermined distance above the surface of the magnetic disk, whereinthe fifth step is performed after the third step.
 4. The method ofmanufacturing a master-information-recorded magnetic disk according toclaim 3, wherein an amount of pressure applied by a lapping materialonto the magnetic disk in a burnishing process in the fourth steppreformed after the first step is higher than an amount of pressureapplied in a burnishing process performed after the second step.
 5. Amethod of manufacturing a master-information-recorded magnetic disk,comprising the steps of: bringing a magnetic disk into close contactwith a magnetic transfer master having a magnetic film formed on atleast one side; magnetically transferring a pattern of the magnetic filmon the magnetic transfer master onto the magnetic disk throughapplication of an external magnetic field to the magnetic transfermaster and the magnetic disk in close contact with one another; andoptically detecting defects in the surface of the magnetic disk, whereinthe magnetic transfer step isperformed immediately after confirming inthe optically detecting step that one of a number of defects on thesurface of the magnetic disk and a size of the defects on the surface ofthe magnetic disk is not greater than a predetermined value.
 6. Anapparatus for manufacturing a master-information-recorded magnetic disk,comprising: contacting means for bringing a magnetic disk into closecontact with a magnetic transfer master having a magnetic film formed onat least one side; transfer means for magnetically transferring apattern of the magnetic film on the magnetic transfer master onto themagnetic disk through application of an external magnetic field to themagnetic disk and magnetic transfer master in close contact with oneanother; and defect detecting means for optically detecting defects on asurface of the magnetic disk, wherein the contacting means and magnetictransfer means perform magnetic transfer immediately after the defectdetecting means has confirmed that one of a number of defects on thesurface of the magnetic disk and a size of the defects on the surface ofthe magnetic disk is not greater than a predetermined value.
 7. A methodof manufacturing a master-information-recorded magnetic disk, comprisingthe steps of: bringing a magnetic disk into close contact with amagnetic transfer master having a magnetic film formed on at least oneside; magnetically transferring a pattern of the magnetic film on themagnetic transfer master onto the magnetic disk through application ofan external magnetic field to the magnetic transfer master and themagnetic disk in close contact with one another; and detecting defectsin the magnetic disk by scanning the magnetic disk with a detection headthat floats a predetermined distance above the surface of the magneticdisk, wherein the detecting step is performed after the magnetictransfer step.